1. Field of the Invention
The present invention relates to a vibration controller and a vibration control method for active vibration insulators, vibration controller and method which can actively inhibit vehicles from vibrating.
2. Description of the Related Art
As disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 2001-140,974, an adaptive control method, for example, an adaptive control method which uses a retarded harmonic synthesizer minimum mean squared filter 50 (hereinafter referred to as “DXHS LMS” filter), has been applied to controlling the vibrations of an engine mount, an automotive active vibration insulator. Specifically, as illustrated in FIG. 7, a sensor retrieves crankshaft rotary pulses and ignition pulsating signals from a vibration generating source 51, such as an automotive engine making a signal source, and corrugates them into a pulsating signal s synchronizing with a control objective signal. Moreover, vibrations generated by the vibration generating source 51 are transmitted into a vehicle passenger room as outer forces by way of a transmission system 52 (G′). A frequency judge 53 converts the pulsating signal s into a sine wave synchronizing with the control objective signal, and turns it into a control objective signal x. An adaptive filter 54 (W) compensates the control objective signal x for amplitude and phase with filter coefficients which are a function of amplitude compensation coefficients and phase compensation coefficients, and outputs it as a cyclic signal y which comprises a sine wave with the compensated amplitude and phase. The cyclic signal y is input into a control objective system 55 (or transmission function G), and is output as a processed signal z by way of the control objective system 55.
After the outer force d, the vibrations of engines, which is transmitted by way of the transmission system 52 (G′), is added to the processed signal z, the sensor detects the processed signal z with the outer force d added as an observed value. Note that the target detection value of sensors is zero in vibration control. Accordingly, the difference between the value by detected the sensor and the target value is an error signal e. A digital filter 57 updates the adaptive filter 54 (W) successively using the error signal e and a value estimated by a control objective system 56 (estimated transmission function Ĝ). The estimated transmission function Ĝ is produced by impulse response measurements and frequency sweeping vibration tests, and is cited when updating the adaptive filter 54.
To summarize, the cyclic signal y is prepared in the following manner. After determining an adaptive filter for every arbitrary rotation number (or frequency). The control objective signal x is compensated for amplitude and phase, and is synthesized into a sine wave signal to result in the cyclic signal y. Then, the resulting cyclic signal y is input into the control objective system 55 (or transmission function G), and is output as the processed signal z. Eventually, the processed signal z controls the outer force d, the vibrations of engines, which is transmitted by way of the transmission system 52 (G′). However, when controlling the vibrations of vibration insulators by adaptive control methods, there arises a problem that the vibration control is so complicated that the cost for the vibration control has gone up.
On the other hand, a simplified vibration control method has been available in which an adaptive control is carried out in compliance with vehicle controllers, though it uses the DXHS LMS filter 50 which operates in the same manner as the above-described adaptive control method. For example, as illustrated in FIG. 7, an optimum filter coefficient is determined for every arbitrary rotation number (or frequency). The resulting optimum filter coefficient data are stored as a data table. The stored data table is retrieved as a ROM 58. Specifically, as illustrated in FIG. 8, a sensor retrieves crankshaft rotary pulses from a vibration generating source 51, such as an automotive engine making a signal source. The frequency judge 53 judges whether retrieved signals are a control objective frequency ω, and selects a control objective signal x of the control objective frequency ω and output the selected control objective signal x. An amplitude/phase compensator 59 compensates the control objective signal x for amplitude and phase with the filter coefficients stored in the ROM 58 as the data table, synthesizes it into a sine wave signal, and outputs a cyclic signal y. A control objective system 55 (or transmission function G) processes the cyclic signal y to output a processed signal z. The resulting processed signal z controls the outer force d, the vibrations of engines, which is transmitted by way of a transmission system 52 (or transmission function G′) As a result, the simplified vibration control method can make the cost for the vibration control less expensive, because it is possible not only to obviate the sensor for detecting vibrations but also to simplify the construction of the controller compared with vibration insulators controlled by the above-described adaptive control method.
In actuality, however, the cyclic signal y is output in the following manner. As illustrated in FIG. 9, a controller unit 31 selects an optimum filter coefficient from a data table ROM 58 depending on input pulsating signals x emitted from engines. Then, the controller unit 31 generates corresponding waveform data out of a waveform storage 32 which stores a waveform table on waveforms, that is, sine wave signals in which distortions resulting from higher order harmonic components are included in advance. Thus, the controller unit 31 outputs the input pulsating signal x as the cyclic signal y. Then, a pulse-width modulated signal generator 40 modulates the cyclic signal y by a pulse-width modulation which changes the amplitude of cyclic waveforms into the pulse width. Thus, the pulse-width modulated signal modulator 40 outputs the cyclic signal y as a pulse-width modulated pulsating signal (hereinafter referred to as PWM signal) p. Moreover, an actuator circuit 42 comprising a so-call H-bridge circuit 43 turns the PWM pulsating signal p into a cyclic-waveform actuating current depending on the signal inversion. The resultant actuating current actuates an electromagnetic actuator 22 of an engine mount which is connected with the output side of the actuator circuit 42. Specifically, an alternate current actuation is carried out in an actuator circuit using direct currents.
As described above, the waveform table stored in the waveform storage 32 does not comprise data on sine waves, but comprises data produced by subtracting higher order harmonic components from sine waves. Thus, waveform storage 32 stores the table on waveforms in which the distortions are included in advance. Accordingly, even when cross-over distortions resulting from pulse-width modulations or distortions resulting from the time constant of electromagnetic actuators are added to the cyclic signal including the aforementioned distortions, these distortions cancel the distortions included in the cyclic signal in advance to remove them. As a result, it is possible to actuate the electromagnetic actuator 22 with an actuating current which is substantially free form distortions. Consequently, the resulting appropriate vibrating forces can inhibit the vibration generating source from vibrating effectively.
Incidentally, when generating the cyclic signal y based on data tables comprising data on sine waves free from distortions, it is possible to generate the cyclic signal y which uses one such a data table comprising data on sine waves free from distortions, even if the frequency, amplitude and phase of the cyclic signal y vary.
However, in the above-described vibration control methods, it is required to use data tables comprising data on waveforms including distortions, instead of data tables comprising data on sine waves free from distortions. It has required a lot of labor to prepare such waveform tables including distortions. Moreover, when generating the cyclic signal y based on such a waveform table including distortions, it has been necessary to use waveform data for every frequency, amplitude and phase of the cyclic signal y. That is, waveform tables should be prepared for each of a large number of the frequencies, or for every type of different vehicles.
Thus, the above-described vibration control methods have required an extremely large amount of labor, because a large number of waveform tables should be prepared, in addition the labor requirement for preparing each of the waveform tables. Accordingly, the above-described vibration control methods have been associated with a problem that the cost for the vibration control has become expensive.